© 2005 Heron Publishing—Victoria, Canada
Effects of seed origin and sowing time on timing of height growth cessation of Betula pendula seedlings
Anneli Viherä-Aarnio (1, 2), Risto Häkkinen (3), Jouni Partanen (4), Alpo Luomajoki (1) and Veikko Koski (1)
1. Finnish Forest Research Institute, Vantaa Research Centre, P.O. Box 18, FIN-01301 Vantaa, Finland / 2. Corresponding author (anneli.vihera-aarnio@metla.fi) / 3. Finnish Forest Research Institute, Unioninkatu 40 A, FIN-00170 Helsinki, Finland / 4. Finnish Forest Research Institute, Punkaharju Research Station, Finlandiantie 18, FIN-58450 Punkaharju, Finland / Received March 12, 2004; accepted June 4, 2004; published online November 1, 2004
Summary
We studied the effects of seed origin and sowing time on height development and timing of height growth cessation of first-year
silver birch (Betula pendula Roth) seedlings in a greenhouse experiment. Seeds of seven origins ranging in latitudes from 58° to 67° N were sown at 1–2-week
intervals eight times from May 21 to July 30, 2001. The day/night temperature in the greenhouse was set at 20/10 °C, but lighting
was natural and day length varied accordingly. Seedling height was measured twice a week. The interaction term between seed
origin and sowing date was significant, but the pattern of height development and timing of growth cessation depended systematically
on latitude of seed origin and sowing date. As seed origin became increasingly northern, growth cessation began earlier and
resulted in shorter growth periods. Later sowing dates delayed growth cessation but also shortened the growth period. Final
seedling height systematically decreased with increasingly northern origins and with later sowings. Linear regression analysis
predicted timing of growth cessation, night length at growth cessation, length of growth period and final seedling height
with high precision when the latitude of seed origin and sowing time were predictor variables. The timing of height growth
cessation was determined by the seed origin, night length and developmental stage of the seedlings.
Keywords:
annual rhythm, climatic adaptation, critical night length, growth period, photoperiod, silver birch, stage of development.
